Water Filters by Concern

Per- and polyfluoroalkyl "forever chemicals" such as PFOA and PFOS.

Treats

Filters certified for PFAS reduction lower PFOA, PFOS and related compounds in drinking water.

Does not solve

They do not address unrelated problems such as hardness scale, sediment, or microbial risk unless separately certified for them.

Certification

Look for NSF/ANSI 53 — and NSF/ANSI 58 for reverse osmosis — carrying a specific PFOA/PFOS reduction claim.

Lead that can enter tap water from service lines and household plumbing.

Treats

Filters certified for lead reduction lower dissolved and particulate lead at the treated tap.

Does not solve

A point-of-use filter treats one faucet — it does not replace a lead service line or home plumbing, and does not address PFAS or hardness unless separately certified.

Certification

Look for NSF/ANSI 53 with a lead reduction claim (tested at pH 6.5 and 8.5).

Calcium and magnesium that cause scale, spotting, and soap problems.

Treats

Water softeners (ion exchange) and conditioners reduce or alter hardness minerals to limit scale.

Does not solve

Hardness is an aesthetic and appliance issue, not a health contaminant; softeners do not remove lead, PFAS, or microbes.

Certification

Cation-exchange softeners are covered by NSF/ANSI 44; performance is described by capacity and grains rather than a contaminant-reduction claim.

Chlorine taste and odor, and disinfection by-products such as trihalomethanes.

Treats

Activated-carbon filters reduce chlorine taste and odor; some are also certified for specific disinfection by-products.

Does not solve

A taste-and-odor carbon filter is not the same as a certified by-product or lead filter, and does not soften water or remove PFAS unless separately certified.

Certification

Chlorine taste and odor is NSF/ANSI 42; specific by-product reduction (e.g. TTHM) is NSF/ANSI 53.

Nitrate and nitrite, often from agricultural runoff, fertilizer, or septic systems.

Treats

Reverse osmosis and certified anion-exchange systems reduce nitrate and nitrite in drinking water.

Does not solve

Activated-carbon filters, pitchers, and water softeners do not remove nitrate — and boiling concentrates it rather than removing it.

Certification

Look for NSF/ANSI 58 (reverse osmosis) carrying a specific nitrate/nitrite reduction claim, or an NSF/ANSI 53 certified anion-exchange unit.

Naturally occurring arsenic that can leach into groundwater across many regions.

Treats

Reverse osmosis and arsenic-selective adsorptive media reduce arsenic at the treated tap.

Does not solve

Carbon filters and softeners do not reliably remove arsenic, and arsenic-III (arsenite) often needs oxidation to arsenic-V before it can be filtered.

Certification

Look for NSF/ANSI 58 with a pentavalent arsenic (arsenic V) reduction claim, and check whether your water carries arsenic III, which needs a pre-oxidation step.

Fluoride, whether added for dental health or naturally elevated in some groundwater.

Treats

Reverse osmosis and activated-alumina systems reduce fluoride in drinking water.

Does not solve

Standard carbon pitchers, faucet filters, and softeners do not reduce fluoride, and boiling concentrates it rather than removing it.

Certification

Look for NSF/ANSI 58 (reverse osmosis) with a fluoride reduction claim, or an activated-alumina unit rated for fluoride.